Re: [TLS] Deployment ... Re: This working group has failed

mrex@sap.com (Martin Rex) Tue, 19 November 2013 00:02 UTC

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To: Joshua Davies <joshua.davies.tx@gmail.com>
Date: Tue, 19 Nov 2013 01:02:24 +0100 (CET)
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From: mrex@sap.com (Martin Rex)
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Cc: Michael Staubermann <Michael.Staubermann@webolution.de>, tls@ietf.org
Subject: Re: [TLS] Deployment ... Re: This working group has failed
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Joshua Davies wrote:
> > You are ware that TLSv1.2 (rfc5246 alone) is weaker than TLSv1.1(rfc4346)?
> 
> Really?  How so?  The only major difference (besides the new cipher suites
> and modes and such) between TLS 1.1 and TLS 1.2 is the PRF - are you saying
> that the TLS 1.1 PRF is stronger than SHA 256?  Has this been proven or is
> that just conjecture?

The TLSv1.1 PRF should be OK for 128-bit signature.

The weakness of TLSv1.2 is in the RSA signatures (digitally signed).
SSLv3, TLSv1.0 and TLSv1.1 were using an SHA1+MD5 combination
for digitally signed, which is stronger than SHA1 alone.

TLSv1.2 substituted this with either (RSA,sha1) or (RSA,md5), and
the latter is pretty far from 128-bit security.

-Martin